Unipass insulation has been used for telephone drop wires. With such an insulation, one compound takes the place of both the insulation and the jacket formerly used in conventional standard cable design. With unipass telephone drop wires of the prior art, however, polyvinyl chloride (PVC) has been the principal ingredient of the insulation.
The unipass telephone drop wire of this invention uses a semi-crystalline, low molecular weight, ethylenepropylene diene terpolymer (EPDM) as the principal insulation ingredient with comparatively small amounts of filler and preferably with fire-retardant ingredients as required by the underwriters. The formulation will be explained more fully in connection with the main body of this specification.
Because of the improved electrical characteristics of this invention, the cross-section of a telephone drop wire can be reduced from 0.160".times.0.300" for the prior art PVC insulation to 0.135".times.0.230" with the EPDM polymer of the present invention, thus saving cost and weight; and the improved drop wire of this invention has other advantages, including better insulation resistance; lower attenuation; higher temperature rating; improved flexibility at low temperature; and excellent mositure resistance which makes the drop wire suitable for burying underground.
Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.